Circuit breaker



R. E. LOCHER CIRCUIT BREAKER Aug. 6, 1957 Filed March l1, 1955 3Sheets-Sheet 1 2 n Nt Rass Loc/fsa,

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United States Patent Oiiice 2,811.2,1'180v Patented Aug. 6, 1957 CIRCUITBREAKER Ross E. Locher, San Marino, Calif., assignor to ZinscoElectrical Products, Los Angeles, Calif., a corporation of CaliforniaApplication March 11, 1955, Serial No. 493,636

9 Claims. (Cl. 200-116) This invention relates toan electric switch andmore particularly to an electric switch of the automatic circuitbreakertype, which may be defined as a device through which an electric currentis passed and which opens the circuit automatically to interrupt thecircuit whenever predetermined conditions occur in the circuit. Theinvention also relates to an automatic circuit breaker which is capableof manual operation to interrupt the circuit.

The invention further relates to a device by which the circuit isinterrupted whenever the current in the circuit increases to apredetermined or overload Value so that it becomes desirable to open thecircuit.

The invention also relates to an overload circuit breaker or interrupterwhich includes a thermostatic element which, when heated above apredetermined temperature by the passage of an excessive amount ofelectrical current therethrough, expands to release an engagement andinterrupt the electrical circuit through the circuit breaker.

It is an object of this invention to provide an improved electricalswitch of the class described in which manual means are provided 4forclosing the switch and opening the switch, the manual means beinginoperative to maintain the switch closed when the thermostatic elementis heated to a predetermined overload state.

A further object of the invention is to provide a circuit breaker inwhich the electrical contacts move into engagement through a rollingaction which assures a good electrical contact.

- Anotherobject of the invention is to provide a circuit breaker inwhich the tripping mechanism is automatically reset when thethermostatic element returns to its normal operating position after acircuit has been interrupted.

The invention also comprises novel details of construction and novelcombinations and arrangements of parts, which will more fully appear inthe course of the following description. However, the drawings merelyshow and the following description merely describes a preferredembodiment and certain modifications of the present invention, which aregiven by way of illustration or example only.

IIn the drawings, wherein like reference characters designate similarparts in the several views:

Fig. l is a front elevational view of one embodiment of the invention;

Fig. 2 is a sectional View taken on the line 2--2 of Fig. 1, showing thecircuit breaker in the closed or on position;

Fig. 3 is a sectional view similar to Fig. 2, showing the circuitbreaker opening when an overload occurs;

Fig. 4 is a partial sectional view similar to Fig. 2, showing thecircuit breaker in the open or off position;

Fig. 5 is a partial sectional View similar to Fig, 2, showing thecircuit breaker being closed;

Fig. 6 is a sectional view taken on the line 6-6 of Fig. 2;

Fig. 7 is a` sectional view taken on the line 7-7 of Fis- 2;

Fig. 8 is an isometric view of the latch of the embodiment shown in Fig.2;

Fig. 9 is a sectional view similar to Fig. 2 of another embodiment ofthe invention;

Fig. 10 is a sectional view taken on the line 10--10 of Fig. 9;

Fig. l1 is a broken sectional view taken on the line 11-11 of Fig. l0;and

Fig. l2 is a similar sectional view showing the operation of the latchdevice illustrated.

A preferred embodiment which has been selected to illustrate theinvention comprises a case or outer housing 20, which is formed of asuitable electrically non-conducting material such as molded plastic.Two terminals 21, 22 are located at opposite ends of the case andprovide for the connection of the circuit breaker into an externalelectrical circuit. Continuity of the circuit between the terminals 21and 22 is maintained through the circuit breaker and is interrupted whenthe circuit breaker is opened automatically or manually.

Mounted within the case 20 and shown as integral therewith is a shaft23. A circular manually operable handle 24 having a thumb lever portion25 extending outwardly from the case 20 is rotatably mounted on theshaft 23. The rotation of the handle 24 is limited by the engagement ofthe thumb lever 2:3 with the case 20 at surfaces 26, 27.

Extending from the terminal 21 within the case 2i) is an electricallyconducting contact arm 30, which is bent to form a leaf spring. Thecontact arm Stb has a fixed contact 31 attached to the end thereof, andit is preferred that the fixed contact 31 have a convex contact surface.

A guide in the form of a slot 32 is provided on the inside of the case20. A Contact carrier 33, which is pref* erably formed of metal, has apin 34 rigidly `att-ached thereto, as by welding. The pin 34 rides inthe slot 32 in the case 20. A second Vcontact 35 is mounted on thecarrier 33. The second contact 35 will be referred to as the movablecontact and is preferably of the same convex shape as the iixed contact31.

A current responsive release element 36, which may be a bimetallicstrip, is attached to the carrier 33. As illustrated, one end of thebimetallic strip 36 is welded between two portions of the carrieradjacent the pin 34. The bimetallic strip 36 is connected to theterminal 22 by a flexible electrical conductor 37.

When the xed contact 31 and the movable contact 35 engage, an electricalcircuit is completed and electrical energy may iiow from the terminal 21through the contacts 31 and 3S, through the current responsive releaseelement 36 and through the exible conductor 37 to the terminal 22. Anarc blowout element 39 is provided adjacent the xed contact 31 to aid inextinguishing any arc produced as the contacts engage or disengage.

The contact carrier 33 is provided with a righteangle extension 40 whichhas a guideway 41. The guideway 41 may be a groove or a slot or thelike, and is shown as an L-shaped lslot of varying width. A pivot pin 42is mounted in the rotating handle 24 and extends through the slot 41. Alatch 43 is mounted on the pivot pin 42 so that the latch 43 may rotatewith respect to the handle 24. The latch 43 is shown separately in Fig.8.

The latch 43 is provided with a boss or cam 44 which engages theguideway 41 of the carrier 33. The latch has an elongated portion 45which is provided with a surface 46 adapted to engage the free end ofthe bimetallic strlp 36, as shown in Fig. 2.

A spring 47 is mounted between the case 2li and the carrier 33 to urgethe contacts out of engagement and to provide a quick opening actionwhen the circuit breaker is tripped due to an overload current. Thespring 47 may be a coil spring attached to a boss 50 on the case and alug 51 extending from the carrier.

Another spring 52 is mounted between the case 20 and the rotating handle24 to bias the handle toward lthe olf or contact disengage position sothat the handle will return to the off position when the circuit breakeris tripped. The spring 52 may -be a coil spring attached to a boss 53 onthe case and a boss 54 on the handle.

The relationship and co-operation of the elements will -be more fullyunderstood from their interaction when the circuit breaker is in use.Referring first to Fig. 2, this shows the circuit breaker in its closedcontact position. The contacts 31 and 35 are engaged and a circuit iscompleted between the terminals 21 and 22 through the current responsiveelement 36. The edge of the slot 41 in the carrier 33 bears against thecam 44 of the latch 43 and tends to rotate the latch in acounterclockwise direction as viewed in Fig. 2. This pressure isproduced by the spring action of the contact arm 30 and by the spring47. Rotation of the latch is prevented by the engagement of the surface46 of the latch with the free end of the current responsive element 36.The pivot pin 42 is to the left of a line extending from the point ofcontact engagement to the center of the shaft 23, hen-ce the forceexerted by the carrier 33 on the latch via the slot and cam acts tomaintain the rotatable handle 24 in the on or contact engaged position.This relation is sometimes referred to as a toggle or over centeraction.

When the current in the bimetallic strip 36 becomes excessive, the stripchanges from its normal shape and bends away from the latch 43, due tothe difference in the coefficients of expansion of the two metalscomprising the strip. The strip 36 co-ntinues to bend until its free endslides out of engagement with the surface 46.

When this occurs, the circuit breaker leaves the static state describedabove and enters a dynamic state wherein the following movements takeplace. The latch rotates counterclockwise to the position shown in Fig.3. The cam 44 moves out of the short arm of the L-shaped slot 41 intothe long arm. The carrier 33 is quickly moved away from the iixedcontact 31 by the action of the spring 47 aided by the arm 30.Simultaneously the handle 24 is rotated clockwise toward the offposition by the action of the spring 52. The movement of the carrier 33away from the fixed contact 31 ceases when the pin 34 reaches the end ofthe guideway 32 4(Fig. 4). The handle 24 comes to rest with the lever 25against the surface 2.6. During the movement, the cam 44 is forced backinto the short arm of the L-shaped slot 41 and the coaction of the camand the wall of the slot rotates the latch 43 clockwise into theposition of Fig. 4 where it is able to engage the bimetallic strip -whenthe latter returns to its normal shape. Thus the circuit breaker is`automatically reset and again ready for use following interruption ofan overloaded circuit.

When the bimetallic strip has returned to its normal condition thecontacts may be again engaged by manually rotating the handle in acounterclockwise direction as shown in Fig. 5. Continued rotation of thehandle urges the surface 46 of the latch 43 into engagement with the endof the bimetallic strip 36 thereby urging the carrier 33 upwardly. Thecontact 35 first tou-ches the contact 31 at a point near theirrespective edges (Fig. 5) and then rolls across the convex surface tothe static engaged position of Fig. 2. The reverse of this action takesplace on disengagement. Thus any pitting and burning due to arcs createdas the contacts touch and part are restricted to the edges of thecontacts and the central portions remain smooth and clean.

Another embodiment of the invention is illustrated in Figs. 9 throughl2. This differs from the previous ernbodirnent in the details of themass employed for controlling the rotation of the latch 43. rIhepivotpin 42 is mounted on the latch 43 and rotates freely in the handle 24. Aportion of the pivot pin is removed where the pin passes through theguideway or slot 41, leaving a section 6u semicircular in cross section(Fig. 11).

A spring 61 is mounted on a boss 62 on the handle 24 and in a notch 63in the carrier 33. The spring 61 urges the carrier 33 away from thecontact arm 30 and also urges the handle toward the o or open circuitposition. A notch 64 is provided in the handle 24 and a matingprojection 65 is provided on the case 20. The circuit breaker is held inthe closed circuit position by the engagement of the projection 65 withthe notch 64 and of the surface 46 with the strip 36.

When in the closed contact position (Figs. 9 and 1l) the edge of theslot 41 bears against the semicircular section 60 at a point 66 andtends to rotate the latch in a counterclockwise direction. As in thefirst embodiment, the engagement of the surface 46 of the latch with thebimetallic strip prevents any movement of the latch.

The movement of the various elements when the circuit breaker is trippedby the bending of the strip 36 is the same as in the first embodimentwith the following exception. The rotation of the latch into a positionto re-engage the strip is accomplished in a different manner. The end 67of the latch opposite the surface 46 is conical in shape. A cam guide 70with a V-shaped groove 71 is attached to the extension 40 of the carrier33. Just after the contacts have been disengaged the latch is in theposition shown as 43a of Fig. l2. As the carrier and handle approach theoff position, the latch moves to the position shown as 43h and theconical end 67 engages the V-groove 71 of the cam guide, and as theelements continue toward the off position, the end 67 and cam guide 70coact to rotate the latch into position for reengaging the bimetallicstrip.

While the invention that has been illustrated and described is nowregarded as the preferred embodiments, the constructions are, of course,subject to modifications Without departing from the spirit and scope ofthe invention. It is, therefore, not desired to restrict the inventionto the particular forms of construction illustrated and described, butto cover all modications that may fall within the scope of the patentclaims.

This application is a continuation-in-part of my copending applicationentitled Circuit Breaker, Serial No. 414,624, filed March 8, 1954.

I claim as my invention:

1. In a circuit breaker, the combination of: a case; a substantiallystationary contact mounted in said case; a movable contact carrierhaving a cam surface and a contact engageable with and disengageablefrom said stationary contact; a manually operable handle rotatablymounted in said case; latch means pivotally mounted on said handle andoperatively connected to said carrier for closing said .circuit breaker,said latch means having a cam; and a current responsive release elementmounted on said carrier and normally engaging said latch means to locksaid latch means and said carrier in fixed relationship, said cam andsaid cam surface coacting to rotate said latch means to re-engage saidlatch means and said release element after said contacts are disengaged.

2. In a circuit breaker, the combination of: a case; a substantiallystationary contact mounted in said case; a movable contact carrierhaving a contact engageable with and disengageable from said stationarycontact, said carrier having a guideway and a cam surface; a manuallyoperable handle rotatably mounted in said case; latch means pivotallymounted on said handle, said pivotal mounting extending into saidguideway, said latch means including a cam for engaging said camsurface; and a current responsive release element mounted on saidcarrier and normally engaging said latch means to lock said latch meansand said carrier in fixed relationship whereby said contacts are engagedwhen said handle is rotated and said contacts are disengaged when saidrelease element is tripped.

3. In a circuit breaker, the combination of: a case;

a substantially stationary contact mounted in said case; a movablecontact carrier having a contact engageable with and disengageable fromsaid stationary contact, at least one of said contacts having a convexsurface, said con* tacts making a rolling engagement, said carrierhaving a cam surface; a manually operable handle rotatably mounted insaid case; latch means pivotally mounted on said handle and operativelyconnected to said carrier, said latch means having a cam for engagingsaid cam surface; and a current responsive release element mounted onsaid carrier and normally engaging said latch means to lock said latchmeans and said carrier in fixed relationship whereby said contacts areengaged when said handle is rotated and said contacts arev disengagedwhen said release element is tripped.

4. In a circuit breaker, the combination of: a case; a substantiallystationary contact mounted in said case; a movable contact carrierhaving a contact engageable with and disengageable from said stationarycontact, said carrier having a guideway including a cam surface; amanually operable handle rotatably mounted in said case; latch meanspivotally mounted on said handle, said pivotal mounting extending intosaid guideway, said latch means including a cam; and a release elementmounted on said carrier, said cam and cam surface coacting to engagesaid latch means and said release element when said contacts aredisengaged, whereby said carrierand said latch means are locked in fixedrelationship and said contacts are engaged by rotating said handle anddisengaged by rotating said handle in the opposite direction and bydisengagement of said latch means and said release element.

5. In a circuit breaker, the combination of: a case having a straightgroove therein; a substantially stationary contact mounted in said case;a movable contact carrier having a contact engageable with anddisengageable from said stationary contact, said carrier having a bossriding in said groove and having a guideway including a cam surface; amanually operable handle rotatably mounted in said case; latch meanspivotally mounted on said handle, said pivotal mounting extending intosaid guideway, said latch means including a cam; and a release elementmounted on said carrier, said cam and cam surface coacting to engagesaid latch means and said release element when said contacts aredisengaged, whereby said carrier and said latch means are locked infixed relationship and said contacts are engaged by rotating said handleand disengaged by rotating said handle in the opposite direction and bydisengagement of said latch means and said release element.

6. In an automatic reset circuit breaker, the combination of: a casehaving a straight groove therein; a substantially stationary contactmounted in said case; a movable contact carrier having a contactengageable with and disengageable from said stationary contact, at leastone of said contacts having a convex surface, said contacts making arolling engagement, said carrier having a boss riding in said groove andhaving a guide way including a cam surface; a manually operable handlerotatably mounted in said case; latch means pivotally mounted on saidhandle, said pivotal mounting extending into said guideway, said latchmeans including a cam; and a release element mounted on said carrier,said cam and cam surface coacting to engage said latch means and saidrelease element when said contacts are disengaged, whereby said carrierand said latch means are locked in fixed relationship and said contactsare engaged by rotating said handle and disengaged by rotating saidhandle in the opposite direction and by disengagement of said latchmeans and said release element.

f7. In a circuit breaker, the combination of: a casing;

' trol member rotatably disposed in said casing; a latch pivotallymounted on said manually actuated control member, said pivotal mountextending into said guideway; a thermostatic element attached to saidcarrier arm and adapted to receive electrical current when said contactsare engaged, said thermostatic element having a free end adapted toengage said latch, said manually actuated control member being adaptedto move said carrier arm and engage said contacts, said free end of saidthermostatic element being adapted when overheated by the flow ofelectrical current to flex away from said latch and become disengagedtherefrom to disengage said contacts; and a first spring attached tosaid manually actuated control member and said casing to bias saidcarrier arm contact away from said fixed contact, said carrier arm andsaid manually actuated control member being in an over center positionwhen said contacts are engaged.

8. A circuit breaker as defined in claim 7 including a second springattached to said carrier arm and said casing to bias said carrier armaway from said lixed contact.

9. ln an automatic reset circuit breaker, the combination of: a casinghaving a pair of terminals; a contact arm disposed within said casing,said contact arm being bent to form a leaf spring and having a contactthereon, said contact being in conductive relation with one of saidterminals; a carrier arm having a contact thereon and a slot including acam surface, said carrier arm being adapted to move toward said contactarm to engage said contacts; guide means disposed within said casing toguide the movement of said carrier arm; a manually actuated controlmember rotatably disposed in said casing; a rst spring attached to saidcasing and said manually actuated control member to bias said carrierarm away from said contact arm; a second spring attached to said casingand said carrier arm to bias said carrier arm away from said contactarm; a latch rotatably mounted on said manually actuated control member,said rotating mount passing through said slot, said latch having a camfor engaging said cam surface; and a thermostatic element secured at oneend to said carrier arm and in conductive relation with the contactthereon, another portion of said thermostatic element being inconductive relation with the other of said terminals, said thermostaticelement having a free end adapted to engage said latch, said manuallyactuated control member being adapted to move said carrier arm to engagesaid contacts when said thermostatic element and said latch are engaged,said free end of said thermostatic element being adapted, whenoverheated, to flex away from said latch and become disengagedtherefrom, permitting said manually actuated control member to berotated and said carrier arm to be moved away from said contact arm todisengage said contacts, said manually actuated control member beingadapted upon rotation in the opposite direction to move said contactsback into engagement, said cam and cam surface coacting to rotate saidlatch and re-engage said ylatch and said thermostatic element.

Sachs July 30, 1940 Johnson June 22, 1943

